Model Noise

Amplifier and Mixer Noise Specifications

You only need to specify noise information for the physical amplifier and mixer blocks that generate noise other than resistor noise. For the other blocks, the blockset calculates the noise automatically based on the resistor values.

You define noise for the physical amplifier and mixer blocks through one of the following specifications:

• Spot noise data in the data source.

• Spot noise data in the block dialog box.

• Spot noise data (rfdata.noise) object in the block dialog box.

• Frequency-independent noise figure, noise factor, or noise temperature value in the block dialog box.

• Frequency-dependent noise figure data (rfdata.nf) object in the block dialog box.

The following table summarizes the noise specification options for each type of physical amplifier and mixer block.

Block	Noise Specification
General Amplifier	Spot noise data (using a Touchstone, P2D, S2D, or AMP data file) OR Spot noise data, noise figure value, noise factor value, noise temperature value, rfdata.noise, or rfdata.nf object in the block dialog box
S-Parameters Amplifier Y-Parameters Amplifier Z-Parameters Amplifier	Spot noise data, noise figure value, noise factor value, noise temperature value, rfdata.noise, or rfdata.nf object in the block dialog box
General Mixer	Spot noise data (using a Touchstone, P2D, S2D, or AMP data file) OR Spot noise data, noise figure value, noise factor value, noise temperature value, rfdata.noise, or rfdata.nf object in the block dialog box
S-Parameters Mixer Y-Parameters Mixer Z-Parameters Mixer	Spot noise data, noise figure value, noise factor value, noise temperature value, rfdata.noise, or rfdata.nf object in the block dialog box

Add Noise to Your System

To simulate the noise of a physical subsystem, you perform the following tasks:

• Specify or Import Noise Data

• Add Noise to the Simulation

Specify or Import Noise Data

The method you use to add noise data to a block depends on whether you are specifying noise data manually or importing spot-noise data.

The following table provides instructions for adding noise data.

Noise Specification	Instructions
Frequency-independent noise figure	In the Noise Data tab of the block dialog box, set the Noise type parameter to Noise figure, and enter the noise figure value in the Noise figure (dB) parameter.
Frequency-dependent noise figure	In the Noise Data tab of the block dialog box, set the Noise type parameter to Noise figure, and enter the name of the rfdata.nf object in the Noise figure (dB) parameter.
Noise factor	In the Noise Data tab of the block dialog box, set the Noise type parameter to Noise factor, and enter the noise factor value in the Noise factor parameter.
Noise temperature	In the Noise Data tab of the block dialog box, set the Noise type parameter to Noise temperature, and enter the noise temperature value in the Noise temperature (K) parameter.
Spot noise data (in a block dialog box)	In the Noise Data tab of the block dialog box, set the Noise type parameter to Spot noise data. Enter the spot noise information in the Minimum noise figure (dB), Optimal reflection coefficient, and Equivalent normalized noise resistance parameters.
Spot noise data (from a data object)	In the Noise Data tab of the block dialog box, set the Noise type parameter to Noise figure and enter the name of the rfdata.noise object in the Noise figure (dB) parameter.
Spot noise data (from a file)	Import file data that includes noise information into the Data file or RFCKT object parameter of the General Amplifier or General Mixer block.

Note

If you import file data with no noise information into a General Amplifier or General Mixer block, the Noise Data tab lets you add noise data manually in the block dialog box.

Add Noise to the Simulation

To include noise in the simulation, you must select the Add noise check box on the Input Port block dialog box. This check box is selected by default.

For information on how the blockset simulates noise, see Model Noise in an RF System.

Plot Noise

RF Blockset™ Equivalent Baseband software models communications systems. The noise in these systems has a very small amplitude, typically from 1e-6 to 1e-12 Watts. In contrast, the default signal power of a Communications Toolbox™ modulator block is 1 Watt at a nominal 1 ohm. Therefore, the signal-to-noise ratio in an RF system simulation is large, making it difficult to view the noise that the RF system adds to your signal.

To display the noise on a plot, you might need to attenuate the signal amplitude to a value within a couple orders of magnitude of the noise.